The present invention relates to a front lay device disposed between a sheet feeder and a printing cylinder of a sheet-fed rotary printing press for holding the leading or gripping end of a sheet in position with respect to a printing plate.
Sheets as delivered one by one onto a feed table by a sheet feeder in a sheet-fed rotary printing press are stopped for positional control by a front lay device located at a front end of the feed table. The sheet is then gripped by a swing gripper mechanism and supplied thereby onto a printing cylinder. The front lay device includes a front stop movable downwardly toward the leading end of the sheet on the feed table. As modern printing presses operate at higher speeds, there is a tendency for a sheet held against the front stop to become unstable. In order to stabilize the sheet, it is necessary to supply sheets at shorter intervals causing the leading end of the next sheet to reach the position of the front stop before the trailing end of the previous sheet is fed out past the front stop. The front lay device having the downwardly movable front stop, however, fails to meet such a requirement.
To meet the high-speed requirement, there have widely been used front lay devices with a front stop movable obliquely upwardly at the front end of a feed table. These front lay devices however cannot be adjusted with ease. When the front lay device is not properly adjusted, sheets cannot be delivered smoothly, and the printing press often needs to be stopped due to improper sheet delivery. Once the printing press is stopped, a large spoilage of paper will occur before the printing press operates under a normal condition.